A CCD type or CMOS type solid-state image sensing device having a large number of photodiodes (PDs) integrated in a surface portion of a semiconductor substrate, and color filters of red (R), green (G) and blue (B) stacked on the PDs respectively has been improved remarkably in recent years. At present, a solid-state image sensing device having millions of PDs integrated into one chip is mounted in a digital camera.
In the solid-state image sensing device, there arise disadvantages in poor efficiency in utilization of light, occurrence of false color, etc. because the solid-state image sensing device is configured so that color filters are used. Therefore, a stack type solid-state image sensing device as described in JP-A-2002-83946 has been proposed as a solid-state image sensing device free from these disadvantages. This stack type solid-state image sensing device is configured so that three photoelectric conversion films for detecting red (R), green (G) and blue (B) light are stacked above a semiconductor substrate in such a manner that signal charges generated in the respective films are accumulated in storage diodes formed in the semiconductor substrate, and that the signal charges accumulated in the storage diodes are read by signal reading circuits such as vertical CCDs and horizontal CCDs formed in the surface of the semiconductor substrate so that the signal charges are transferred. According to the stack type solid-state image sensing device, a high-quality image can be generated while the aforementioned disadvantages are eliminated.
FIG. 11 is a partly sectional typical view of the stack type solid-state image sensing device according to the background art.
As shown in FIG. 11, a p-well layer 102 is provided in a surface portion of an n-type semiconductor substrate 101. An n+ region 106 and an n region 107 are formed in a surface of the p-well layer 102 so as to be slightly apart from each other. A photoelectric conversion film 103 stacked above the n-type semiconductor substrate 101 is electrically connected to the n+ region 106 by a wire 104. A transfer electrode 105 is provided on the n region 107 so that the transfer electrode 105 serves also as a reading electrode which reaches the n+ region 106. When a read pulse is applied to the transfer electrode 105, a signal charge reading region is formed between the n+ region 106 and the n region 107. Signal charge accumulated in the n+ region 106 is read to the n region 107. The signal charge accumulated in the n region 107 is then transferred.
FIG. 12 is a view typically showing a potential transition state in the partial section of the stack type solid-state image sensing device shown in FIG. 11. A left part of FIG. 12 shows a state in which a read pulse is not applied to the transfer-electrode 105. A right part of FIG. 12 shows a state in which a read pulse is applied to the transfer electrode 105. In FIG. 12, “Low” expresses a low potential portion, and “High” expresses a high potential portion. As the number of contour lines surrounding “Low” increases, the potential of the low potential portion decreases.
As shown in FIG. 12, when a read pulse is applied to the transfer electrode 105, signal charge e-accumulated in the n+ region 106 is poured into the n region 107 through the surface portion of the n-type semiconductor substrate 101 and accumulated in the n region 107.